Substitute Column Name From Variable For Select Query?

In a select query, I want to substitute the column name from a variable (In turn from an array of column names). Details are given below. I am getting an error as mentioned below.

Create table Test1(IDNumber(10),
Namevarchar2(100),
Descriptionvarchar2(1000),
Sitevarchar2(100));

Insert Into Test1 values(10,'Thomas','Manager','LA');
Insert Into Test1 values(11,'George','Chairman','LA');

declare
MTest1Test1%RowType;
str1VarChar2(1000):='Name';
MValue1Varchar2(100);
begin
Select * Into MTest1 from Test1 where ID=10;
str1:='Select MTest1.'||str1||' from dual';
execute immediate str1 into mvalue1;
dbms_output.put_line('mvalue1 '||mvalue1);
end;
/

I am getting the error:

ORA-00904: "MTEST1"."NAME": invalid identifier
ORA-06512: at line 9